1. Technical Field
The present invention pertains to a mailing machine, and in particular to a pusher on a timing belt used as part of a mail inserter.
2. Description of Related Art
A mailing machine is equipment used to build up a mail piece from its components: the individual pages of the mail piece and its envelope. In the course of this building up process, several collated pages of a mail piece, called a collation, are conveyed by a conveyor between stations of the mailing machine. In a mail inserter type of mailing machine, as the collations are transported along the conveyor, they are eventually stuffed into an envelope. As a way of providing to the mailing machine a known position on the conveyor of at least one edge of each page of a collation, i.e. to provide edge registration, the upstream end of each collation is pushed by fingers protruding from the conveyor; these fingers are called pushers.
FIG. 1a shows part of a prior art inserter-type mailing machine, for document collating and stuffing. It includes a conveyor segment 41 formed by a pair of chains 42, 43, each chain trained about two sprockets 44, 45 and 46, 47 respectively. Each sprocket is secured to the end of a shaft 48, 49. Each of the chains 42, 43 has a plurality of pushers 51 extending outwardly from one of the chains 42, 43. Pairs of the pushers 51, one on each chain 42, 43, push documents 52 along the conveyor segment 41. In this prior art mailing machine, the documents 52 rest on a platform 53.
Sometimes, although a conveyor continues to turn so as to convey downstream its burden of collations, ajam or other situation obstructs the collations. The obstruction causes a jamming or backlogging of the collations. When a high speed mailing machine senses such a backlogging, it automatically performs a controlled halt. Although this halting may be performed rapidly, there is still a significant risk that some collations will be damaged by being forced against either the initiating obstruction itself or a secondary obstruction, one caused by the initiating construction.
What is needed is a way of pushing a collation along a timing belt so as to register the upstream end of the collation, but doing so with a mechanism that responds to a backward force exerted by the collation, in case of the collation encountering an obstruction, in such a way as to avoid damaging the collation.